Detecting Changes in Population Trends for Cook Inlet Beluga Whales Using Alternative Schedules for Aerial Surveys
Population growth rates, birth interval and rates of survival
Measuring population trends, and detecting a change in the trend, of Cook Inlet beluga whales (Delphinapterus leucas), has a specific role in the co-management agreement that determines harvest levels, and a more general application in the management of the population. Currently, an annual aerial survey schedule has provided abundance estimates from which growth trends for this population are determined. Under the harvest co-management agreement, the measured trend over a 10-year period is used to classify the population into one of three growth categories ('high', 'intermediate', or 'low'; Appendix). The growth category, along with the average abundance over the last 5-year period, is used to determine the number of takes allowed over the next 5-year hunting period (Appendix). For a more general application, we would like to be able to detect a change in the growth rate of the population that results from a change in the underlying life history parameters such as birth interval and rates of survival and identify the year that the change occurred.